Testicular Steroidogenesis in the Common Marmoset, Callithrix jacchus

Abstract

Studies were undertaken to determine the primary pathway of testicular biosynthesis of androgens in Callithrix jacchus, the common marmoset. Testicular fragments (25 mg) were incubated at 37 C in Krebs-Ringer bicarbonate buffer, pH 7.4, with pregnenolone-7-³H (10 µCi; 20 Ci/mm) or with progesterone-7-³H (10 µCi; 24 Ci/mm). Duplicate fragments were incubated with each substrate for 30 min, or for one, three and five hours, for a total of 16 individual incubations. Metabolites were separated by paper and thin-layer chromatography and their identity was established by recrystallization to constant specific activities and ³H/¹⁴C ratios. Pregnenolone was metabolized primarily to progesterone, with some conversion to 17α-hydroxyprogesterone, 20α-dihydroprogesterone, androstenedione, and testosterone. Progesterone was converted to 17α-hydroxyprogesterone, with some conversion to 20α-dihydroprogesterone, androstenedione, and testosterone. A substantial amount of the progesterone substrate was not metabolized throughout the incubation period. These data suggest a predominant delta-4 pathway in the testis of Callithrix, with possible defective 17α-hydroxylase activity.